Munoz took over as CEO of Chicago-based United in September aiming to build morale after years of strained labor relations. He replaced Jeff Smisek, who resigned because of probes into United's relationship with the Port Authority of New York.

Munoz has plenty of work cut out for him.

United had the worst customer satisfaction of any North American airline, with the exception of low-cost carrier Frontier, according to J.D. Power's 2015 ranking.